Inactivation of Salmonella typhi in an aquatic microcosm by plasma-actived water generated by creeping arc discharge: Importance of the cellular physiological state

Conventional disinfection methods often generate toxic by-products, highlighting the need for alternative methods. The present study evaluated the antimicrobial efficacy of plasma-activated water (PAW), generated by creeping arc discharge, on Salmonella Typhi in aquatic microcosms, with a focus on the role of bacterial physiological states. Bacterial suspensions were prepared from lag, exponential, stationary, and decline phases. PAW was produced at different activation times (PAW [5 min], PAW [10 min], PAW [15 min] and PAW [20 min]). Its impact was assessed at various contact times (15, 30, 45 and 60 min) and treatment volumes (2 mL, 3 mL, 5 mL, and 10 mL). Results revealed that PAW induced significant reductions in cultivable S. Typhi cells, with complete inactivation achieved after 45 and 60 min exposure depending on the growth phase. The lag phase and decline phase exhibited the highest susceptibility. PAW [5 min] showed minimal disinfection across all time points, confirming that short activation durations are insufficient for effective microbial control during the lag phase. Increasing PAW activation time and volume positively correlated with higher inhibition rates. Physicochemical characterization indicated that bactericidal activity was driven by reactive oxygen and nitrogen species (RONS) and by progressive acidification of the medium. The Chick–Watson model and analysis of Log Removal Values confirmed the bactericidal efficacy of plasma-activated water (PAW) across all growth phases of Salmonella typhi . Overall, this work demonstrates that PAW is a promising and sustainable disinfection technology for waterborne pathogens.